A microcapsule is a small sphere, or core, with a uniform wall around it. The wall, or shell, around the core is usually a polymer. The core can be a suspension of solids, liquid or other microcapsules. In one use, microcapsules allow the controlled release of the material comprising the core in response to various stimuli. Other uses may not require release of the encapsulated material. It is this characteristic that gives microcapsules so many uses in many different industries.
Thus, microcapsules can be used to form a pressure sensitive adhesive (“PSA”), particularly for use with labels and tapes. A PSA allows for a controlled release of the adhesive, only when pressure is applied. A significant advantage of a PSA over other adhesives is the ability to be completely non-sticky until pressure is applied to break the microcapsules. In addition, pre-coating screws, nuts, and bolts with microcapsules can allow for a faster and more efficient manufacturing process. Workers will not have to take time to cover screws, for example, in a liquid sealant. Instead, they will only have to insert a PSA coated screw normally. The force applied while attaching the screws will activate the PSA.
Microcapsules can also be used to create an epoxy-based self-healing coating, in other words a self-healing coating in which epoxy resin is used along with a catalyst or hardener (an amine in this case). Such a self-healing coating involves a system that embeds two sets of microcapsules distributed throughout a host coating matrix. One set of microcapsules contains an epoxy resin and the other set of microcapsules an amine based hardener. If a microcrack propagates through the coating, it ruptures both sets of microcapsules in its path, releasing their contents to mix and react with each other for self-healing. Such a self-healing coating may be significantly lower in cost than currently existing alternative self-healing coatings.
However, animes are soluble in both water and organic solvents. Thus, it is very challenging to encapsulate them. There are a number of examples in the prior art of encapsulation of some material by an amine based shell. This is the opposite of the present invention in which polymer shells encapsulate an amine in an aqueous environment. Also, U.S. Pat. No. 4,521,352 describes the encapsulation of an aqueous solution containing amine groups. However, it describes an interfacial polymerization between the amine component and another component to form a shell. The reaction to form the shell is reacting away the amine component. Furthermore, it describes the encapsulation of a water solution that has some amine groups. The present invention is a system for encapsulating an amine that does not react away any of the amine during the encapsulation.